In recent years, the communication type by telephones have become diversified. In addition to conventional speech communication by circuit switch, telephones which are able to perform packet communications utilizing IP (Internet Protocol) networks are being widely utilized. For example, there is “chat mail” where mobile phones swap e-mail in real time conversation (see Patent Document 1). Chat mail is one of the types of communication called “group communications” where members registered in advance form a group and reciprocate text and other data each other in real time.
In group communications, in general, one terminal in the group becomes sender and the other terminals become receivers for one to multi communications. When a plurality of terminals participate in communications, it is convenient if the terminal side can grasp what members are participating in the communications at present. Therefore, in for example the system disclosed in Patent Document 2, a server apparatus managing the group communications provides each terminal with a list of participating members which is displayed on a display part of each terminal.
In such group communications, Speech communication has been attempted by utilizing VoIP (voice over Internet Protocol). One of these is called “PoC (push to talk over cellular)”. In PoC, an SIP (session initiation protocol) server manages groups and members in groups and performs call control of packetized audio (see Patent Document 3).
In PoC, a terminal ending group communications, as disclosed in for example Patent Document 3, transmits a request for ending communication to the server apparatus managing the communication. When receiving this ending request, the server apparatus performs a predetermined procedure for ending the group communication of the terminal and notifies the fact that the communication has ended by completion of the procedure to the requesting side terminal.    Patent Document 1: Japanese Patent Publication (A) No. 2005-18423    Patent Document 2: Japanese Patent Publication (A) No. 2005-136524    Patent Document 3: Japanese Patent Publication (A) No. 2005-518166